The industrial gas industry is faced with ever more stringent requirements for purity in industrial gases for research and for industries, such as the electronic fabrication industry.
Oxygen is one of the contaminant gases for which tight specification requirements have been set by such industries, particularly for inert gases used for blanketing or prevention of oxidation. Oxygen impurity levels must be very low in such gases which are used for inerting atmospheres. Typically, those gases include nitrogen and argon. Other gases which face similar specifications include carbon monoxide, hydrogen, carbon dioxide, fluorine, chlorine and water.
In the purification, storage and dispensing of industrial gases, it is necessary to check or monitor purity on a batch or continuous basis. When the levels of impurities in gases is very low, such as parts per million (ppm) or parts per billion (ppb), and the monitoring of the gases for impurities is done in a batch or non-continuous basis, difficulties arise in having rapid, reproducible, accurate results. Effectively, it is difficult to reach a steady state condition.
Although it is possible to at least partially overcome this problem by using a dedicated analyzer, when the detection requires a sophisticated and/or expensive detection device, such as a gas chromatograph, the trend is to use such detection equipment for a plurality of analyses, so that it is impossible or impractical to reach a steady state for any particular impurity analysis.
The art has recognized that the adsorbent used in gas chromatographs for oxygen analysis can have improved performance if initially subjected to a singular oxidation treatment. This is reported in U.S. Pat. No. 4,744,805 and 4,713,362.
Removal of oxygen from bulk gases, in contrast to analysis, is described in U.S. Pat. No. 4,747,854.
The prior art has failed to achieve a solution to the problem of analysis of trace levels of interactive gases, such as oxygen, in gases requiring high purity specifications. The present invention provides an inexpensive method for trace level interactive gas, (i.e., oxygen,) impurity detection in gases using gas chromatography that is particularly valuable in non-steady state situations. The method is fast, accurate and sensitive to interactive gas, (i.e., oxygen), levels in the ppm and ppb range. This overcomes a problem that has existed for years that has prevented reproducible analysis.